Curling die set



W. RICHTER CURLING DIE SET Filed. Oct. 21. 1965 Dec. 17, 1968 FIG.5 e

INVENTOR.

Richter Walfer ATTORNEY United States Patent 3,416,475 'CURLIN G DIE SET Walter Richter, Syosset, N.Y., assignor to Regina Enterprises, Inc., New York, N.Y., a corporation of New York Filed Oct. 21, 1965, Ser. No. 500,130 Claims. (Cl. 113-1) ABSTRACT OF THE DISCLOSURE This disclosure is directed to a drawing die set which includes relatively movable complementary reciprocating die members mounted for movement toward one another. The forming station defined in the respective die members to form a collared hole in a sheet material having a curled end comprises a hole size holding means carried on one of the die members which is adapted to be received within the collared opening of the work piece, disposed between the die members to maintain the size thereof during the curling operation, and a complementary curling means carried on the other of said die members.

The arrangement is such that the holding means and complementary curling means is such that as the two are moved toward one another a curl is formed on the free end of the collar. Means are also provided for eifecting an adjustment of the relative position between the size holding means and the curling die means to effectively vary the overall height or length of the curled edge portion of the collar defined thereby for various designs considerations. The arrangement of the adjustment is such that the same can be readily efiected without causing the removal of the die members from the press.

This invention relates in general to a drawing die set, and more specifically, to a drawing die set having a particularly constructed forming station for curling collared holes in sheet material.

In the manufacture of fin tube heat transfer units adapted for heating and/or cooling, it is important that the fins be accurately spaced longitudinally of the tube carrying the heating and/ or cooling medium. In the appli cation of such fin tube units for baseboard radiation or heating, it has been discovered that the optimum spacing of fins is from 8 to 14 fins per inch; that is, that a spacing between fins ranging from .125" to .071". In such fin tube units, the attachment of the fin is heat transfer relationship to the tube is obtained by expanding the tube into a collared opening formed in the fin. Accordingly, the fin is formed with a collared opening in which the height of the drawn collar is utilized to space the fins one from another along the length of the tube.

Heretofore, it has been customary in forming such fins with collared openings on a draw press wherein the collar is extruded as the hole is formed. As the same die means forming the extruded collar always form the collar to the same height in each fin formed thereby, it was heretofore necessary to utilize diiferent dies to effect a change in the collar length if the spacing between adjacent fins was varied to meet specific design considerations; or to utilize an auxiliary means to effect a change in the collar height of such fins to obtain the desired range of spacings for various design considerations. Since the requirement of difierent dies for each specific collar length proved to be a costly investment and time consuming operation, the most common and expedient manner heretofore used for changing or varying the collar height of a fin to vary the longitudinal spacing of such fins along a given tubular member, was to flare the outer end of the collar outwardly until the overall length or height of the straight portion of the collar, plus the flared end portion thereof defined the re- Patented Dec. 17, 1968 "ice quired overall height or length of the collar to determine the desired spacing between adjacent fins in a given fin tube installation. For example, if a fin formed an unflared collar height or length of .145" was required to be spaced along the tube at spacings of .125", the end of the unflared collar was fiared an amount sufficient to reduce the overall length thereof to the required .125 However, experience has shown that the degree of flaring to which the collar could be subjected to was limited. For example, if a .145" collar height was flared outwardly to define an overall collar height of less than .091, that is, sized so as to accommodate 11 fins per inch, the degree of flaring required would be so acute that the collar would likely crack. If such collar cracked on flaring to reduce the overall length thereof, such cracks usually propogated into the straight portion of the collar thereby making that fin deficient in its heat transfer characteristics upon the expansion of the tube into the collared hole. Such cracking also adversely affected the degree of attachment or bond between the tube and the fin when the tube was expanded into the collared opening. As a result, considerable difficulty was encountered in tooling for the manufacture of such fins to meet the numerous design requirements of such fin tube units.

In the conventional forming of collared holes for use in fin work, the flare above described was formed by driving a conical flaring punch downwardly internally against the top of the open collar thereby causing it to flare angularly outwardly the required amount to produce the desired overall collar height or length for a given fin spacing application. Accordingly, the inherent disadvantages of the prior known methods were that they were incapable of producing a full range of collar heights on a single die.

It is therefore an object of this invention to provide an improved die structure wherein a full range of collar heights is rendered possible on a single die set.

Another object of this invention is to provide an improved die construction which permits the end of the collar to be reversely bent or curled upon itself so that the eifective overall height or length of the collar about an opening in a sheet material can be varied in accordance with the degree of curl imparted to the end portion thereof.

Another object of this invention is to provide an improved draw die which can be eifectively adjusted to form a collar height to any desired length so that a single die is capable of accommodating a full range of collared heights.

Another object of this invention is to provide an improved die construction wherein the effective length of the collar formed in the sheet material can be varied without removing the die from the press.

Another object of this invention is to provide a die set capable of providing a full range of collar heights in which the adjustment can be affected and maintained to a very high degree of accuracy.

Another object of this invention is to provide an improved die set which can be individually adjusted while the press in which the die is being employed is either stopped or running.

Another object of this invention is to provide an innproved die construction capable of accurately forming collar hole'sizes to enhance ease of assembly of the fin blanks to a tube.

Another object of this invention is to provide an improve-d die construction which will result in a collared opening having enhanced strength characteristics and as when heat transfer characteristics when a tube is expanded thereto.

Another object of this invention is to provide a draw die set which is capable of resulting in fins having collared openings of precise length or height so that the fins per unit length of tube can be accurately accounted for, and thereby enable exact duplication of fin blanks possible to provide for optimum uniform heat transfer rating from coil to coil.

In accordance with this invention, the foregoing objects, and other features and advantages of this invention are attained in a drawing die set which includes a fixed plate and a complementary reciprocating die plate mounted for movement toward and away from the fixed plate. The forming station defined in the respective die plates to form a collared hole in a sheet material having a curled end comprises essentially of a hole size holding means carried on one of the die plates and which is adapted to be received within the collared opening of a work piece disposed therebetween to maintain the size thereof during the curling operation and a complementary curling means is carried on the other of said die plates. The arrangement of the size holding means and complementary curling means is such that as the holding means and curling means are moved toward one another, a curl is formed on the free end of the collar. Means are also provided for alfecting an adjustment in the relative position between the size holding means the curling die means to effectively vary the overall height or length of the curled collar for various design considerations. In accordance with this invention, the eifective length or height of the collar can be atfected simply by controlling the degree of curl formed on the collar of the opening in a sheet material. The arrangement of the curling means with respect to its die plate is such that the same can be readily adjusted by an adjusting tool means without causing the removal of the die plate from the press. Means are also provided for positively maintaining the set or adjusted position of the die.

It is therefore a feature of this invention to provide an improved forming die wherein the collar of an opening is curled at the end thereof an amount required to produce the desired overall collar length for a given fin spacing.

Another feature of this invention resides in the provision of a means for curling the end of the collar in which the elongation of the overall collar height can be held within acceptable limits and free of cracks.

Another feature of this invention resides in the provision of forming a fin with a collared opening having either a partial or full curl form about the end of the collar to result in a greatly strengthened collar construction having enhanced heat transfer characteristics when a tube is expanded thereinto.

Another feature of this invention resides in a die set for forming curled collar openings which can be readily adjusted to control overall curled collar heights formed thereby with a minimum of effort and a maximum of r ease, and with a minimum of lost time.

Another feature of this invention resides in the provision of a die set for forming curled collared openings which is relatively simple in construction, which can be readily fabricated, and which is positive in operation.

Other features and advantages will become more readily apparent when considered in view of the specification and drawings in which,

FIGURE 1 illustrates a plan view of a fin formed with a curled collar which is constructed on the die set of the instant invention.

FIGURE 2 illustrates the utilization of the fin construction of FIG. 1 in a fin tube unit as adapted for use in a radiation unit of a baseboard radiator.

FIGURE 3 is an enlarged detail cross section of a fin construction formed on the die set of the instant invention wherein a partial curl is formed on the collar about the fin opening.

FIGURE 4 is a view similar to that of FIG. 3 but illustrating a full curl formed on the collar for effectively reducing the overall height of the finished fin collar for various design considerations.

FIGURE 5 illustrates a fragmentary showing of a die set utilizing the concept of the instant invention to form the curled end collar, and having parts thereof shown in section.

FIGURE 6 illustrates a sectional view of an adjusting tool adapted to adjust the setting of the curling die of FIG. 5, and

FIGURE 7 is an enlarged detail showing of the curling die head in accordance with the instant invention.

Referring to the drawings, there is shown therein a fin tube unit 10 and fin 11 of the type disclosed in a copending application, Ser. No. 500,129 filed Oct. 21, 1965, entitled, Fin Tube Unit. Essentially, the fin tube 10 disclosed is adapted for use, for example, as a radiation unit in a baseboard heating installation. Essentially, the fin tube unit 10 comprises an elongated tube 12 through which a heating medium may flow. A plurality of substantially rectangularly formed fins 11 are secured at longitudinally spaced intervals along the tube 12 in heat transfer relationship.

As shown in FIGS. 1 through 4, each of the respective fins 11 are formed with an opening 13 which is circumscribed by a collar 14, the latter being utilized, in the illustrated embodiment of FIG. 2, to define the spacing between adjacent fins spaced along the length of the tube 12. As shown, the free end of the collar 14 of each fin is reversely bent to define a curl 15. The purpose of the curl 15 is to enhance the strength characteristics of the collar 14 surrounding the fin opening and to enhance the heat transfer characteristics of the fin when the tube is expanded into the opening thereof. Also, the curl 15 of the collar 14 provides an effective means whereby fins having standard collar lengths or heights can be utilized in a full range of design considerations wherein the spacing between adjacent fins is desired to be varied in accordance with particular design considerations.

In order that the collar 14 of the fin 11 be formed to any desired overall height with a single die, there is provided in accordance with this invention, an improved die construction whereby the same may be accomplished. Referring to FIG. 5, there is shown therein, a die set 16 which comprises a fixed die plate 17 and a movable die plate 18 which may be placed in a suitable die press (not shown). The die set 16 embodying the instant invention is of the type disclosed in a co-pending application, Ser. No. 495,178 filed Oct. 12, 1965, wherein the fin construction of FIG. 1 may be progressively formed in a series of forming stations formed in the die set. As described in the co-pending application, Ser. No. 495,178 filed Oct. 12, 1965, the die set is provided with a plurality of forming stations wherein the work piece or sheet material W from which the fin is formed is progressively advanced from station to station as the stock sheet material is formed to the finished fin construction of FIG. 1. To effect the advancement of the sheet material W from station to station in an accurate and positive manner, a pull through feed system, as described in said co-pending application, Ser. No. 495,178 filed Oct. 12, 1965, is also utilized in the construction of the die set 16 embodying the forming station of the instant invention.

Since the curling operation of this invention is effected in the last forming station of the die set, and since the instant invention is limited to the curling station of the die set, only this portion of the die set is illustrated in FIG. 5, as only this portion of the die set 16 is necessary to effect the understanding of the present invention.

The complementary forming portions of the die set 16 usually positioned in a suitable press and they are carried on a pair of complementary die plates 17 and 18. Accordingly, the die set is provided with a series of progressive die forming stations, as for example, one or more drawing stations, piercing stations, and in accordance with this invention, a curling station 19. The arrangement of the respective stations is such that the curlin-g station constitutes the last station of the die set. Accordingly, one die plate 17 is fixed in a suitable manner on a die set shoe 20, which in turn is supported on the bed 21 of the press. The complementary die plate 18 is suitably connected to the ram of the die press (not shown) for movement toward and away from the fixed die plate 17. As shown, the punch plate 22 of the die set is connected to the movable die plate 18, and a stripper plate 23 is resiliently supported from the punch plate 23.

In accordance with this invention, the curling station 19 is disposed immediately downstream from the last drawing station in which the collared opening 24 in the sheet material W is formed. The forming station defining the curling station 19 of the die set 16 includes a complementary size holding means 25 for maintaining the exact size of the collared hole 24 formed in the work sheet W or sheet material, and a complementary curling die head 26 for affecting the curl on the end of the collar 24 as the die plates 17, 18 close one on the other.

As best seen in FIG. 5, the size holding means is mounted in a bore 25A formed in the stripper plate 23. It comprises a bushing 27 rigidly secured within the bore 26 of the stripper plate, and it carries the size holding plug 28. As shown, the holding plug 28 is movably mounted within the bushing 27 by means of a pin 29 and cage slot 30 connection. A spring means 31 interposed between the top of the plug 28 and the bushing 27 to exert a bias on the plug which normally tends to urge it toward its extended position, as shown in FIG. 5. Since the plug 28 forms a lap fit with the internal bore of the bushing 27, an air venting hole 32 is spaced above the plug in the top of the bushing. Accordingly, the plug 28 is free to move inwardly of the bushing 27 as the respective dies plates 17, 18 close on one another as will be hereinafter described. If desired, the sizing plug 28 is provided with a small radius on its bottom circumferential edge to provide ease of entry into the collared hole 24 in the sheet material W for accurate pick up of the hole. Accordingly, as the dies close on one another, the size holding plug 28 enters into the collared hole 24 and thereby supports the side wall of the collar from the inside thereof to prevent the collapse under the curling pressure applied thereto.

The curling die 26 complementing the size holding means 25 is located in vertical alignment therewith in the bottom die plate 17. Accordingly, it will be noted that the bed 21 of the press, the die set shoe 20 resting thereon, and the bottom die plate 17 are provided with openings or bores 21A, 20A and 17A respectively. It will be noted that the opening or bore 20A formed in the die set shoe 20 is provided with internal threads 20B and a diameter which is less than the bore 17A formed in the die plate 17 housing the curling head of the curling die, and the bore 21A in the bed 21 of the press. Accordingly, the curling die 26 is mounted in the bore 17A of the bottom die plate 17, which in turn is supported on the bottom die shoe 20.

In accordance with this invention, the curling die head 26 is mounted for limited vertical movement within the bore 17A of the bottom die plate 17. Vertical movement is limited by means of a retaining pin 33 which projects into an angular groove 34 formed about the body of the die head 26. As shown, the clearance between the pin 33 and the groove 34 is such as to permit limited vertical movement of the die head 26 for adjustin'g purposes within bore 17A. The arrangement is such that when the curling die 26 is in its full up position the overall collar height which is formed thereby is the shortest that can be produced in the die. Also the arrangement is such that the top 26A of the curling die 26 will not exceed or extend beyond the top surface of the bottom die plate 17 in the upper most position thereof. The vertical movement of the sizing plug 28 in turn is set at the face of the top stripper plate 23.

It is important that the top surface 26A of the curling die 26 not extend above the di e plate 17.

In the most down position of the curling die head 26 bottoms on the die set shoe 20. In this position, it provides the highest collar length that can be produced with the specific die set. Accordingly, it will be noted that the clearances between the retaining pin 33 and the groove 34 about the body of the curling die determines the limits of the collar heights or lengths which can be curled in the instant die set.

Referring to FIG. 7, it will be noted that the curlin die 26 comprises a die body which is provided with a fiat raised center portion 26A which is circumscribed by an angular groove 26B, which in the illustrated embodiment as being substantially semi-circular in cross section. Accordingly, the circumference of the raised portion 26A of the die 26 is substantially equal to the internal diameter of the collared opening 24 formed in the sheet material W.

To effect adjustment of the curling die body 26 without effecting removal of the die set from the die press, there is provided an adjusting means whereby the die head 26 can be vertically'adjusted within the bore 17A of the bottom die plate 17. As seen in FIG. 5, a curling die adjusting screw 35 is connected to the die body 26 by means of a retaining pin 36. As shown, the adjusting screw 35 is provided with external threads which are adapted to engage the internal threads 20B of the die set shoe 20. Accordingly, it will be noted that by etfecting rotation of the adjusting screw 35 is in one direction or the other, the connected die head 26 will be vertically adjusted accordingly.

To lock the adjusting screw 35 in the adjusted position thereof, the adjusting screw 35 is provided with plastic or resilient inserts 37 which will frictionally maintain the adjusting screw 35 is the adjusted position thereof, as such inserts 37 will engage the threads 2013.

As shown, the top of the curling die body 26 is provided with a broached female hex hole 38 to facilitate the removal of the die 26 from the bottom die plate 17. Also, the bottom of the die body 26 is provided with a broached female hex hole 39 for receiving the male hex end 4-0 of the adjusting screw 35, and the lower end of the adjusting screw 35 is provided with a female broached hex opening 41 formed and adapted to receive the male hex head 42 of an adjusting tool 43 as will be hereinafter described.

Accordingly, an important feature of the invention resides in the provision of an arrangement which permits the adjusting of the curling die 26 without removing the die set from the press. Accordingly, the vertical adjustment of the curling die body 26 can be accomplished from below the bed 21 of the press, and this setting adjustment may be made while the press is either stopped or in operation. The adjusting means by which the curling die 26 is adjusted comprises a tool 43 which is adapted to be inserted through the opening 21A in the bottom of the press bed and the aligned threaded opening 20A in the die set shoe 20. Accordingly, the adjusting tool 43 comprises a shaft 44 having a male hex end 42 which is adapted to be received in the female hex opening 41 located in the bottom of the adjusting screw 35. Connected to the shank 44 of the tool is a turn knob 45 and a connected scale means 46. Rotatably journalled about the shank 44 of the tool 43 is a sleeve 47 which has a pointer 48 connected thereto. The pointer 48 is adapted to complement a scale means 46 connected to the shank. Accordingly, the scale means 46 may be proportioned in accordance with the number of threads formed in the bore of the die shoe plate 20 so that by setting the indicator or pointer 48 of the rotatable sleeve 47 to a given setting on the scale means 46 and rotating the turn knob 45 to bring the setting and pointer in alignment, the amount of vertical adjustment can be readily determined. Accordingly, when the male 'hex 42 on the wrench 43 is engaged with the female hex hole 41 of the adjusting screw 35, the turning of the wrench 43, either clockwise or counterclockwise, will effect the rotation of the adjusting screw 35 accordingly. When the wrench 43 is turned clockwise looking up from the bottom, the curling die 26 is moved vertically upwardly to decrease the collar height by increasing the degree of curl, e.g. as shown in FIG. 4. When the tool is turned counterclockwise, the curling die body '26 moves vertically downward to increase the collar height by decreasing the degree of curl as in FIG. 3. To effect the adjustment the sleeve and pointer of the adjusting means is rotated to a major scale division on the wrench. The sleeve 47 is then held stationary while the wrench 45 is actuated and the movement of the wrench, relative to the pointer 48, allows vertical movement in either the up or down direction to be read directly. If desired, the adjusting screw threaded may be chosen at threads per inch which provides for 50 thousands vertical motion per Wrench revolution. The scale 46 on the wrench 43, in turn, may have fifty divisions on its circumference with major scale divisions at 0, 10, 20, 30, 40, etc.

In order to hold the position of the curling die 26 at any setting, the adjusting screw is provided with at least two plastic inserts 37 to lock the screw in the tap hole at whatever set position.

In operation, it will be noted that with the vertical position of the curling die body 26 adjusted, whenever a work piece W formed with a collared opening 24 is inter- K posed between the sizing means 25 and the curling die means 26 at the curling die station, that th movement of the hole sizing holding means 25 into the collar opening 24 causes the work piece W to be moved downwardly toward the curling die body 26. Accordingly, as the sizing means and curling die body close one on the other, the end portion of the collar 24 is reversely bent due to the curvature of the circumscribing groove 26B of the die head 26 to reversely bend the end portion thereof. Accordingly, depending on the adjusted position of the die body 26, the curled end defined will either be formed as a partial curl, as shown in FIG. 3, a full curl as shown in FIG. 4, or any degree curl therebetween. Accordingly, it will be noted that the overall finished length or height of the collar can be varied depending upon the degree of curl, which in turn is dependent upon the vertical adjustment of the die body 26. Accordingly, a fin constructed by the forming die described is such that a collared opening 24 formed thereon is provided with strength characteristics and heat transfer characteristics which are superior to those fins having a simply constructed collared opening.

While the instant invention has been described with respect to a particular embodiment thereof, it will be readily understood and appreciated that variations and modifications of the invention may be made without departing from the spirit or scope thereof.

What is claimed is:

1. In combination with a drawing die set including a fixed die plate and a complementary reciprocating die plate mounted for movement toward and away said fixed die plate, the improvement of a forming station for shaping a collared hole in sheet material comprising,

a hole size holding means carried by one of said die plates which is adapted to be received within the collared opening of a workpiece disposed between said die plates,

and complementary curling die means carried by the other of said die plate adapted to curl the free end of said collar of said opening as said hole size holding means and complementary curling die close on one another,

said hole size holding means comprises,

bushing, 21 size holding plug snugly fitted in the end of said bushing, said plug being sized to the collared hole in said sheet material so as to prohibit collapse of said collar in shaping the same,

a spring means exerting a bias on said plug, and means for retaining said plug within said bushing for limited movement.

2. The invention as defined in claim 1 wherein said curling die means comprises,

(a) a curling die body having a raised fiat top adapted to complement said plug,

(b) said die body having a groove circumscribing said raised flat top thereof,

(c) said other die plate having a bore therein adapted to receive said curling die body,

(d) and means for effecting adjustment of said die body within said bore relative to said size holding means to vary the overall collar height shaped thereby.

3. In combination with a drawing die set including a fixed die plate and a complementary reciprocating die plate mounted for movement toward and away said fixed die plate, the improvement of a forming station for shaping a collared hole in sheet material comprising,

a hole size holding means carried by one of said die plates which is adapted to be received within the collared opening of a workpiece disposed between said die plates,

and complementary curling die means carried by the other of said die plate adapted to curl the free end of said collar of said opening as said hole size holding means and complementary curling die close on one another, and including means for effecting limited adjustment of said curling die means relative to said hole size holding means to effectively vary the overall height of the curled collar formed thereby accordingly,

whereby said adjusting means comprises,

an adjusting screw connected to said curling die body means for effecting vertical adjustment of said die body relative to said hole size holding means,

and an adjusting tool adapted to engage said curling die adjusting means to vertically adjust its position relative to said hole size holding means.

4. The invention as defined in claim 3 wherein said tool includes,

(a) shank having a means connected on the end thereof to engage said adjusting screw,

(b) a sleeve mounted on said shank for relative rotation thereto,

(c) a pointer connected to said sleeve, and,

(d) a scale connected to said shank whereby co-action between said sleeve and shank accurately determines the degree of adjustment between said curling die means and said hole sizing holding means.

5. A drawing die set comprising,

(a) fixed die plate means adapted to seat on a bed of a die press,

(b) said fixed die plate means having a bore therein disposed in axial alignment an opening in the bed of said press,

(c) a movable die plate means adapted to be mounted for reciprocal movement toward and away said fixed die plate means,

(d) a punch plate carried by said movable die plate means,

(e) a stripper plate operatively associated with said punch plate,

(f) a forming means including a size holding means for maintaining the size of a collared opening formed in a sheet material carried on said stripper plate, and a complementary curling die for curling the end of the collar circumscribing an opening in said sheet material carried,

(g) said size holding means including a sizing plug 9 sized to the collared opening of said sheet material movably mounted on said stripper plate,

(h) a spring means exerting a bias on said plug for normally projecting the same beyond the end of said stripper plate,

(i) a curling die mounted in the bore of said fixed die plate,

(j) said curling die having a head portion formed with a circumscribing groove which is substantially semicircular in cross section, and

(lg) means for rendering said die head vertically adjusted within said bore.

6. The invention as defined in claim wherein,

(a) said latter means includes a threaded screw,

(b) means for detchably connecting said screw to said die head portion,

(c) said screw being threaded in a tapped hole in said die set shoe to effect adjustment of said die head,

(d) means for limiting the adjustment of said die head within said bore,

(e) and a tool for effecting the adjustment of said die head.

7. The invention as defined in claim 6 and including means to lock said threaded screw in the tapped hole of said die set shoe in the adjusted position of said die head.

8. The invention as defined in claim 7 wherein said lock means includes resilient inserts in said screw to frictionally secure said screw in the adjusted position thereof.

9. A drawing die set comprising,

(a) a die set shoe having a threaded opening extending therethrough, said die set shoe being adapted to rest on the bed of a die press having an opening in axial alignment with said threaded opening,

(-b) fixed die plate adapted to seat on a die set shoe,

(c) said fixed die plate having a bore therein disposed in axial alignment with a threaded opening of said die set shoe,

(d) a movable die plate mounted for reciprocal movement toward and away said fixed die plate,

(e) a punch plate carried by said movable die plate,

(f) a stripper plate operatively associated with said punch plate,

(g) and a forming station defined by an opening in said stripper plate disposed in axial alignment with the bore in said fixed die plate,

(h) a hole size holding means for maintaining the size of a collared opening formed in a sheet material carried in the opening of said stripper plate, and a complementary curling die for curling the end of the collar circumscribing the opening in said sheet material carried in the bore of said fixed die plate,

(i) said size holding means including a bushing rigidly secured in the opening of said stripper plate,

(j) a sizing plug sized to the collared Opening of said sheet material movably mounted in the end of said bushing,

(k) a spring means exerting a bias on said plug normally projecting the same beyond the end of said stripper plate,

(1) a pin and slot connection for maintaining said plug mounted within said bushing for limited movement relative thereto,

(m) said curling die having a head portion defined by a raisedflat top and a circumscribing groove which is substantially semi-circular in cross section,

(n) means for rendering said die vertically adjusted within said bore,

(0) said latter means including a threaded screw,

(p) means for detachably connecting said screw to said die head portion,

(q) said screw being threaded in a tapped hole in said die set shoe to effect adjustment of said die head portion,

(r) means for limiting the adjustment of said die head portion within said bore,

(s) and a tool for effecting the adjustment of said die head portion toward and away said size holding means.

10. In combination with a drawing die set including a fixed die plate and a complementary reciprocating die plate mounted for movement toward and away said fixed die plate, the improvement of a forming station for shaping a collared hole in a sheet material comprising,

a hole size holding means carried by one of said die plates which is adapted to be received within the collared opening of a workpiece disposed between said die plates,

References Cited UNITED STATES PATENTS 2,944,502 7/ 1960 Lemmerz 72354 CHARLES W. LANHAM, Primary Examiner.

R. D. GREFE, Assistant Examiner.

US. Cl. X.R. 

